Elastomer rebound, jounce and related compression springs

Abstract

A bellows shaped compression spring having a variable spring rate and formed of an elastomer having tensile characteristics such that the ratio of plastic strain to elastic strain is greater than 1.5 to 1, said spring being particularly adapted for use in the strut assemblies of light weight, low profile automobiles for minimizing noise, vibration and impact forces otherwise transmitted from the wheel to the vehicle body.

We claim: 
     
       1. In an vehicle strut assembly having a housing, a piston and piston rod extending through said housing and interconnecting the vehicle body to the wheel assembly for damping the vehicle spring system, an improved rebound bumper compression spring comprising: a) an elongated member formed of an elastomer having a ratio of plastic strain to elastic strain that is greater than 1.5 to 1, said member being mounted in said strut assembly so as to attenuate noise, vibration and road shocks;   b) said member having wall sections and connecting angles to define a bellows shape;   c) the molecular structure of the walls and angles of said member being oriented as a result of plastic deformation of said member in at least one direction;   d) the dimensions of said member being such that the ratio of the combined height of two adjoining wall sections to the thickness of the wall is less than 17;   e) the thickness of said walls increasing over a substantial portion of the length of the elongated member in order to provide a variable spring rate; and   f) said member having a length so as to cushion said spring system upon rebound for a distance of greater than 3 millimeters and to provide for an initial soft spring rate for a portion of its travel and a higher spring rate for the remainder of its travel.   
     
     
       2. A rebound bumper spring as recited in claim 1 in which said bellows unit is deformed by precompression by more than 30% of its length in order to induce a compression set to which the spring will thereafter spring back in operation. 
     
     
       3. A compression spring as defined in claim 1 in which said member is cylindrical in shape. 
     
     
       4. In a vehicle strut assembly having a housing, a piston and piston rod extending through said housing and interconnecting the vehicle body to the wheel assembly for damping the vehicle spring system, an improved rebound bumper compression spring comprising: a) an elongated member formed of an elastomer having a ratio of plastic strain to elastic strain that is greater than 1.5 to 1, said member having wall sections joined by connecting angles that define substantially an apex;   b) the molecular structure of the member being oriented as a result of some plastic deformation of said member in at least one direction;   c) the dimensions of said member being such that the ratio of the combined height of two adjoining wall sections to the thickness of the wall does not exceed 17; (and)   d) said member having a length so as to cushion said spring system upon rebound for a distance of greater than 3 millimeters and to provide for an initial soft spring rate for a portion of its travel and a higher spring rate for the remainder of its travel; and   e) said member being mounting in said strut assembly surrounding said piston rod so as to attenuate noise, vibration and road shocks.   
     
     
       5. A compression spring as recited in claim 4 in which a) said member is formed of wall sections and connecting sections having an accordion-like cross sectional configuration;   b) the dimensions of said member along at least a portion of its length being variable in order to provide a variable spring rate; and   c) the molecular structure of the member being oriented as a result of some plastic deformation in its axial direction and in its radial direction.   
     
     
       6. A compression spring as defined in claim 4 in which the dimensions of the wall sections and the thickness of the wall sections are varied so as to provide a variable spring rate. 
     
     
       7. A compression spring as defined in claim 4 in which member is cylindrical and has a variable diameter in order to provide a variable spring rate. 
     
     
       8. A compression spring formed of an orientable thermoplastic elastomer comprising; a) an elongated member formed of an elastomer having a ratio of plastic strain to elastic strain that is greater than 1.5 to 1;   b) said member having wall sections and connecting angles to define a bellows shape;   c) the molecular structure of the walls and angles of said member being oriented as a result of plastic deformation of said member in at least one direction, said plastic deformation being substantially equal in all of the angles;   d) the dimensions of said hollow member being such that the ratio of the combined height of two adjoining wall sections to the thickness of the wall is less than 17; and   e) said connecting angles of said member progressively increasing from a minimum of 30° to a maximum of 160° to provide a variable spring rate.   
     
     
       9. A compression spring as defined in claim 8 in which said member is cylindrical. 
     
     
       10. A compression spring formed of an orientable thermoplastic elastomer comprising: a) an elongated member formed of an elastomer having a ratio of plastic strain to elastic strain that is greater than 1.5 to 1, said member being formed of a plurality of substantially straight wall sections joined by connecting sections having radii sufficiently small to approximate an apex;   b) the molecular structure of the member being oriented as a result of some plastic deformation of said member in at least one direction;   c) the dimensions of said member being such that the ratio of the combined height of two adjoining wall sections to the thickness of the wall does not exceed 17, and   d) said connecting sections joining said wall sections at progressively increasing angles from a minimum of 30° to a maximum of 160° to provide for a variable, non-linear spring rate.   
     
     
       11. A compression spring as recited in claim 10 in which a) said member is formed of wall sections and connecting sections having an accordion-like cross sectional configuration;   b) the dimensions of said member along at least a portion of its length being variable in order to provide a variable spring rate; and   c) the molecular structure of the member being oriented as a result of some plastic deformation in its axial direction and in its radial direction.   
     
     
       12. A compression spring as defined in claim 10 in which the dimensions of the wall sections and the thickness of the wall sections are varied so as to provide a variable spring rate. 
     
     
       13. A compression spring as defined in claim 10 in which member is cylindrical and has a variable diameter in order to provide a variable spring rate.